Method for making reticulated structures

ABSTRACT

Method for making reticulated structures by periodically contacting adjacent streams of a series of generally like streams of flowable material as they are extruded along sinuous paths, and thereafter setting the extruded under the same pressure streams.

nited States Patent Fairbanks [54] METHOD FOR MAKING RETICULATEDSTRUCTURES [72] Inventor: Theodore H. Fairbanks, Liverpool,

[73] Assignee: FMC Corporation, Philadelphia, Pa. [22] Filed: July 17,1970 [21] Appl. No.: $5,835

Related US. Application Data [63] Continuation-impart of Se'r. No.778,134, Nov.

22, 1968, Pat. No. 3,577,587.

[52] US. Cl. ..264/167, 264/177, 264/237, 264/DIG. 81

[51] Int. Cl. ..B29c 25/00, B291 3/00, DOId 5/20 [58] Field of Search..264/167, DIG. 81, 177, 171, 264/237 [56] References Cited UNITEDSTATES PATENTS 3,012,275 12/1961 Nalle,Jr. ..18/12 1 Aug. 8, 19723,384,692 5/1968 Galt et a1 ..264/ 167 3,019,147 1/1962 Nalle, Jr...264/DIG. 81 2,919,467 1/1960 Mercer ..264/ l 67 FOREIGN PATENTS ORAPPLICATIONS 380,369 9/1964 Switzerland ..264/DIG. 81

Primary Examiner-Robert F. White Assistant Examiner-Jeffery R. ThurlowAttorney-Thomas R. O'Malley, George F. Mueller and Eugene G. Horsky [57]ABSTRACT Method for making reticulated structures by periodicallycontacting adjacent streams of a series of generally like streams offlowable material as they are extruded along sinuous paths, andthereafter setting the extruded under the same pressure streams.

4 Claims, 9 Drawing Figures METHOD FOR MAKING RETICULATED STRUCTURESThis application is a continuation-in-part of my application Ser. No.778,134, filed Nov. 22, 1968, now US. Pat. No. 3,577,587.

The present invention is directed to an improved method for makingreticulated structures by extrusion.

US. Pat. No. 2,919,467 is directed to the manufacture of net-likestructures in which the mesh intersection-forming portions are eachcomposed of an integrally extruded plastic mass and the meshstrandforming portions are divisions of such intersectionformingportions, with the whole fabric or structure being an integrallyextruded entity. The net-like structure produced by this method variesin thickness, with the portions at which the strands intersect beingtwice the thickness of the strands themselves. As a result, such fabricslack flexibility and are not wholly suitable for many uses, as forexample as bonded reinforcements for sheets or films.

US. Pat. No. 3,019,147 discloses an apparatus for making fiat netting byextruding plastic material through a plurality of spaced nozzles inwhich adjacent nozzles are periodically swung toward each other so thatthe streams extruded therefrom can weld together without crossing. Suchapparatus requires numerous moving parts, nozzles which are ofcomplicated construction and is not entirely suitable for makingextremely fine mesh netting. Accordingly, a primary object of thisinvention is to provide a generally new or improved and moresatisfactory method for making net-like structures and fabrics.

Another object of this invention is the provision of a method capable ofproducing reticulated structures having fine mesh openings.

Still another object is the provision of an improved method for makingreticulated structures of honeycomb construction by extrusion.

A further object is the provision of an improved method for makingreticulated structures at high rates of speed.

These and other objects are accomplished in accordance with the methodof the present invention in which a series of generally like, spaced,unconfined streams of fiowable material are continuously extruded undersubstantially the same pressure, with each extruded stream moving alongan individual sinuous path and with the sinuous paths of adjacent ofsuch streams being 180 out of phase with each other in frequency and ofsuch amplitude as to cause such adjacent streams to periodically contactwith each other and thereby form junctions. The extruded streams andjunctions are then set to provide an integral reticulated structure. Theunconfined streams are all extruded within a single surface, the termsurface being employed throughout the description and claims in itsgeneral sense as a two-dimensional locus of points and thus includesboth planes and curved (e.g. cylindrical) surfaces.

Desirably, the amplitude of the sinuous paths of adjacent streams isonly such as to insure contact between such streams and will depend, ofcourse, on the spacing between such adjacent streams. The frequencytogether with the amplitude of the sinuous paths of the extruded streamswill determine the size of the openings in the resulting reticulatedproduct.

Preferably, all of the extruded streams are of like frequency andamplitude.

The extruded streams are of generally like cross-section and may be, forexample, round, rectangular or perhaps oval in configuration. Thestreams of flowable material may be considerably greater in width thanin thickness, or of ribbon shape, to provide reticulated structureswhich are of honeycomb construction.

The apparatus employed in the method of the present invention includes ahousing into which a fiowable material is delivered under pressure andwhich has spaced opposing walls which together define an extrusionorifice. A series of spaced partitions are positioned within thehousing, between the opposing walls thereof, and terminate at leastwithin the housing opening. Each of these partitions has surfaces whichextend transversely of the housing opening together defining anextrusion orifice. Preferably, but not necessarily, at least portions ofthe opposing surfaces of adjacent of such partitions extend inconverging relationship in the areas adjacent to their free ends.

The apparatus also includes means for providing relative longitudinalmovement between adjacent partitions so that each projects beyond theother in alternate relationship. Preferably, such means reciprocate thepartitions longitudinally relative to the housing and the walls definingthe housing opening, with alternate of the partitions moving in unisonand substantially out of phase with the partitions which are adjacentthereto. To insure proper control over the shape and direction of theextruded streams, the partitions are preferably not projected beyond oroutwardly of the housing opening during their reciprocation. Suitablemeans are provided outwardly of the housing opening for setting thefiowable material which issues from the extrusion orifices.

More particularly, the converging portions of the opposing surfaces ofadjacent partitions define lips, the inner faces of which are preferablyof concave configuration in a longitudinal direction of the respectivepartitions. These converging portions may be spaced from each other sothat they, together with the walls of the housing opening, define anextrusion orifice of rectangular configuration. This spacing between theconverging portions of adjacent partitions may be considerably less thanthe width of the housing opening so that the stream of fiowable materialwhich is extruded therefrom is in the form of a narrow ribbon.Alternatively, the opposing surfaces of each pair of adjacent of thepartitions may be formed with opposing grooves extending longitudinallythereof in the areas adjacent to their free ends. These grooves are ofconcave cross-section and together define an orifice of generallyannular configuration. Moreover, these grooves may be of a width equalto or less than the width of the housing opening and, at the free endsof the partitions, extend in converging relationship with each other.

In the operation of the above-described apparatus, fiowable materialrides along the longitudinally concave portions or lips of the alternatepartitions which are in their lowermost positions and is extruded as aseries of individual streams. All of such streams are directeddownwardly and laterally, with alternate of such streams moving in thesame lateral direction and opposite to the lateral movement of thestreams adjacent thereto. As the free ends of the partitions which areadjacent to such alternate partitions next assume lowermost positions,the continuity of the extruding streams is unbroken. However, thelongitudinal concave portions of these now projecting partitions causethe streams to reverse their lateral direction of travel. With continuedrelative movement between adjacent partitions so that each projectsbeyond the other in alternate relationship, the extruded streams arecaused to assume sinuous paths. The pressure applied to the flowablematerial is, of course, sufficient to insure that adjacent extrudedstreams periodically contact with each other as they move along theirsinuous paths.

The concavity formed along the converging portions of the opposingsurfaces of adjacent partitions will determine the trajectory of theextruded streams, with the greater the concavity of such convergingportions the greater the horizontal component of such streams.

The opposing surfaces of the partitions, which at least assist indefining the extrusion orifices, are preferably formed of or coated witha substance which is not readily wet by the fiowable material beingextruded. For example, such opposing surfaces may be coated withpolytetrafluoroethylene resin when employed in extruding a moltenthermoplastic material such as polyethylene.

The teachings of the present invention are applicable for use with avariety of fiber-forming materials, which are referred to by the termsplastic" and fiowable strand-forming materials, including polyolefins,such as polyethylene, polypropylene, polybutylene, polystyrene,polystyrene-acrylonitrile blends, acrylonitrile butadiene-styreneblends, acrylonitrilebutadiene copolymers, polybutene, polyisobutylene,polyisoprene, and isobutylene-isoprene copolymers; halogenated olefins,such as polyfluoroethylene, polychlorofluoroethylene,polychlorofluoropropylene, polyvinyl chloride, polyvinylidene chloride,polyvinyl chloride-acetate copolymer, polyvinyl chloridepolypropylenecopolymer, polychloroprene, fluoroinated ethylene-propylene copolymers,vinylidene fluoride-chlorotrifluoroethylene copolymers, and vinylidenefluoride-hexafluoropropylene copolymers; polyesters, such aspolyethylene terephthalate and copolymers thereof and polycarbonate;polyamides, such as polyhexamethyl adipamide, polycaprolactam,polyhexamethylene sebacamide, poly -amino-undecanoic acid; polyvinylacetates; chlorinated polyethers, such as, ethylacrylatechloroethylenevinyl ether copolymer; acrylic resins, such as polyacrylonitrile,polyacrylates and methacrylates; natural rubbers; compounded silicones;polyurethanes; polyethers, such as polyformaldehyde,formaldehyde-ethylene oxide copolymers, and polytrioxane; polysulfurresins, such as polysulfones and polysulfides; water-soluble, alkalisoluble, and organic solventsoluble cellulose esters and ethers, such ascellulose nitrate, cellulose acetate, cellulose butyrate, cellulosepropionate, ethyl cellulose, viscose or cellulose xanthate,cuproammonium cellulose, and carboxymethyl cellulose; glasses; metals,etc. Such materials may include various additives such as stabilizers,dyes, foaming agents, etc., if so desired.

It will be apparent that the manner by which the extruded junction andmesh-strand forming streams are set will depend upon the particularmaterial which is being employed.

For a greater understanding of the invention, reference is made to thefollowing detailed description and drawing, in which FIG. 1 is avertical section taken longitudinally of the apparatus employed in themethod of the present invention;

FIG. 2 is a transverse vertical section taken substantially along theline II-II of FIG. 1;

FIG. 3 is a fragmentary view illustrating elements of the apparatusshown in FIG. 1 in one position during operation;

FIG. 4 is a view similar to FIG. 3 showing the elements in anotherposition during operation of the apparatus;

FIG. 5 is a view similar to FIGS. 3 and 4 showing the elements in stillanother position during operation of the apparatus;

FIG. 6 is a horizontal section illustrating a portion of the apparatusshown in FIG. 1;

FIG. 7 is a view similar to FIG. 6 illustrating another modification ofthe apparatus shown in FIG. 1;

FIG. 8 is a view similar to that shown in FIG. 5 illustrating a stillfurther modification of the apparatus shown in FIG. 1; and

FIG. 9 is a diagrammatic view showing a reticulated structure formedwith an apparatus as illustrated in FIG. 8.

With reference to FIGS. 1 and 2 of the drawing, the apparatus employedin the method of the present invention includes a housing 15 having achamber 17 into which a fiowable strand-forming material is deliveredunder pressure through an inlet 19. Side walls 21 and 23 and end walls25 and 27 of the housing 15 together define an elongated opening 29.

A series of partitions or extrusion elements 31 are positioned withinthe housing 15, between the side walls 21 and 23, and terminate withinthe housing opening 29. The opposing surfaces 33 of adjacent partitions31 are uniformly spaced from each other along the major portion of theirlengths and converge at 35 to provide lips 37 at the free ends of suchpartitions. The portions 35 of the partition surfaces 33 are preferablyof concave configuration, as illustrated, but may be shaped to providefor a more gradual convergence between opposing of such surfaces. In theposition of the partitions 31 shown in FIG. 3, the lips 37 of adjacentpartitions 31 are in contact with each other.

Extending at least along each of the arcuately converging portions 35,and preferably longitudinally along a substantial portion of each of thepartition surfaces 33, is a groove 39 which is of generally uniformdepth and of arcuately concave and, more particularly, semi-circularconfiguration. As shown in FIG. 6, the grooves 39 in opposing partitionsurfaces 33 together define an extrusion orifice 41 between thepartition lips 37, with such orifice having a diameter which is onlyslightly smaller than the thickness of the partitions themselves.

The partitions 31 are mounted within the housing 15 for relativelongitudinal movement whereby the free end of each partition may bealternately projected and retracted beyond the free end of a partitionwhich is directly adjacent thereto, as shown in FIGS. 4 and 5.

This may be accomplished by longitudinally reciprocating alternatepartitions 31 while the partitions adjacent thereto are maintainedstationary. More preferably, all of the partitions 31 are simultaneouslyreciprocated in a longitudinal direction, with alternate partitionsmoving in the same direction and opposite to the partitions 31 which areadjacent thereto. Thus, as any one of the partitions 31 is moving towardthe exit of the housing opening 29, the partitions 31 on either sidethereof are concomitantly being retracted. As more fully describedhereafter, the extent to which the free ends of the partitions areprojected beyond the free ends of the partitions which are adjacentthereto may be varied. Generally, the partitions 31 should not beprojected outwardly of the exit end of the housing opening 29.

The desired reciprocation of the partitions 31 may be achieved by avariety of different means. One such means is illustrated in FIGS. 1 and2 of the drawing and includes a crank shaft 43 and crank arms 45. Theends of the crank shaft 43 are rotatably supported by and extend beyondthe housing end walls 25 and 27. A driving force may be applied toeither or both ends of the crank shaft 43 by suitable means, not shown,to rotate the same at a uniform rate of speed. A cylindrical bearing 47is formed at one end of each of the crank arms 45 which rides on thecrank shaft 43. The opposite ends of the individual crank arms 45 arehinged by pins 49 to the partitions 31.

The crank shaft 43 is shaped to impart continuous reciprocating motionsimultaneously to all of the crank arms 45 and the partitions 31 whichare hinged thereto, with alternate of such partitions 31 being in phaseand 180 out of phase with the partitions 31 which are adjacent thereto.

In the operation of the above-described apparatus a flowable or plasticstrand-forming material, such as molten polypropylene, is deliveredunder pressure through the housing inlet 19 to fill the chamber 17,including the portions thereof between and around the partitions 31.Assuming that the partitions 31 are in positions as shown in FIG. 3, themolten polypropylene will issue from the extrusion orifices 41 as aseries of laterally spaced vertical streams located in substantially thesame surface or plane.

As the crank shaft 43 is rotated, alternate of the partitions 31 areprojected toward the exit end of the housing opening 29 while thepartitions 31 which are adjacent thereto are retracted into positions asshown in FIGS. 1 and 4. During such movement, the arcuate portions 35 ofthe partitions 31 which are being projected exert a lateral force uponthe molten polypropylene which flows relative thereto. Thus, the streamsof molten polypropylene issuing from between adjacent partitions aregradually deflected laterally from their original vertical paths withoutinterrupting the continuity of such streams.

As shown in FIG. 1, alternate of these deflected streams 51, 53, 55 and57 are directed along similar paths which intersect with the paths ofthe respective adjacent streams 59, 61, 63 and 65. The more pronouncedthe convergence between the portions 35 of opposing partition surfaces33, the greater will be the lateral deflection of the extruding streams.The degree to which such extruded streams are deflected in the lateraldirection is one factor which will determine the mesh pattern of theresulting reticulated structure.

The pressure applied to the flowable or plastic material must besufficient to insure that the extruded streams, which are alongintersecting paths, contact and bond with each other as indicated at 67.Excessive pressure may cause distortion of such streams at theirlocations of contact and should be avoided.

Upon movement of the partitions 31 from their positions shown in FIG. 4to that shown in FIG. 5, the extruding streams change their directionsof lateral travel, with each stream now following a path which isgenerally parallel to the paths heretofore assumed by the adjacentstreams. In other words adjacent extruded streams which had traveledalong converging or intersecting paths, such as the streams 51 and 59,now assume diverging paths, while the adjacent streams which heretoforehad diverging paths, such as the streams 53 and 59, now assumeconverging paths.

As the streams which are extruded along their newly assumed pathscontact and bond with each other, as indicated at 69, the partitions 31are again reciprocated into positions as shown in FIG. 4. It will beapparent that by moving the elements 31 alternately into positions asshown in FIGS. 4 and 5, each of the extruded streams follows a sinuouspath, with the paths of adjacent streams being 180 out of phase witheach other in frequency. The amplitude of the individual sinuous paths,which is determined primarily by the concavity of the portions 35 of thepartition surface 33 and the pressure applied to the material beingextruded, is such that the adjacent extruded streams periodicallycontact with each other.

Any suitable means may be positioned below the housing 15 to set theextruded streams into a reticulated structure. When extruding moltenthermoplastic material, such means may be, for example, a nozzle asshown at 71 for discharging chilled air against the extruded and bondedstreams.

In lieu of the arrangement described above, the partitions 31 may besubstantially thicker than the diameter of the extrusion orifice whichis formed between adjacent of such partitions. This modification, asillustrated in FIG. 7, provides for significant contact and thus bettersealing between the opposing surfaces of adjacent partitions 31.

As heretofore mentioned, extrusion orifices may be shaped to provideextruded streams which are round, rectangular or perhaps oval incross-section. A modification of the above-described apparatus forproviding extruded streams of rectangular cross-section is shown in FIG.8 and includes partitions 73 which are considerably greater in widththan the spacing between adjacent of such partitions. Adjacent of suchpartitions 73, together with the side walls 21 and 23 of the housing 15,define extrusion orifices which are greater in length than in width sothat flowable or plastic material issuing therefrom is of ribbon-likeform. While the operation of the apparatus shown in FIG. 8 issubstantially the same as that heretofore described, the resultingreticulated structure is of honeycomb construction, as indicated at 75in FIG. 9.

Iclaim:

1. Method of making a reticulated structure including the steps ofcontinuously extruding each of a series of generally like, spaced,unconfined streams of flowable strand-fonning material along anindividual sinuous path with the successive portions of each of suchreticulated structure.

2. A method as defined in claim 1 wherein all of the sinuous paths areof like frequency and amplitude.

3. A method as defined in claim 1 wherein each of the extruded streamsare rectangular in cross-section, with its width being greater than itsthickness whereby the resulting reticulated structure is of honeycombedconstruction.

4. A method as defined in claim 1 wherein said streams are of generallycircular cross-section.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CDRRECTION Patent No. t 3Dated August I 8, 1972 Inventor-( TheOdOre H. Fairbanks It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below: v

In the ABSTRACT OF THE DISCLOSURE, line 4, after "extruded" insert-under the same pressure-;

line 5, delete "under the same pressure",- line 5, after "extruded"insert --streams-.

Signed and sealed this 9th day of January 1973.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. Attesting Officer ROBERT GOTTSCHALK Commissionerof Patents

2. A method as defined in claim 1 wherein all of the sinuous paths areof like frequency and amplitude.
 3. A method as defined in claim 1wherein each of the extruded streams are rectangular in cross-section,with its width being greater than its thickness whereby the resultingreticulated structure is of honeycombed construction.
 4. A method asdefined in claim 1 wherein said streams are of generally circularcross-section.